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Studies of a Quenched Cupola Part IV: Behavior of Coke (11-12#01)

Coordinator: University of Antiqua, S. Katz Associates and AFS Melting Methods & Materials Division (8)

The cupola furnace produces about 60% of liquid iron used for castings. Despite the age of the process, over 200 years, the cupola has maintained its position as the predominant melting furnace because it is able to melt a much wider vari- ety of scrap than the more modern electric furnaces, hence providing iron at lower cost. Today’s cupolas are far different than the original furnaces which were carried on the back of a horse drawn platform to produce iron for itinerant pot- makers. The virtue of this furnace is its ability to transform itself to meet current needs.

Today the cupola furnace must transform itself once more to insure its continued use. There are two major problems that need to be solved: (1) the cupola furnace burns coke which generates more carbon emissions than any other foundry process. As a result, future emissions legislation could impose severe penalties on cupola melting. Since the thermal efficiency of coke-combustion is only 50% - 65%, a significant reduction in emissions could be provided by improving the combustion efficiency. (2) The cupola furnace supplies a large fraction of the carbon for alloying, however the efficiency of coke dissolution is very low (5% - 10%). As a result the required amount of coke required for iron production increases significantly when there is a need for alloy-carbon.

The cupola furnace is among the most complex processes employed in the foundry. All the easy improvements have already been made. Further improvements will require a more sophisticated understanding of the complex internal processes. To this end, the Department of Energy and the American Foundry Society sponsored a project to water- quench a cupola furnace while in full operation and then to conduct an archeological examination of the contents. Three papers were published in 2009 covering the details of the quenching experiment, and tracing the changes in the iron, steel, silicon carbide and slag from the charge door to the tap-hole. The current and final paper covers the corre- sponding changes in coke, the material whose use must be reduced in order to reduce carbon emissions. It is anticipat- ed that this study will generate ideas for the improvement of cupola performance which includes cost and energy savings and improved combustion efficiency.

A recent research project, commissioned by Committee 8K, measured all of the properties used to describe both foundry and blast furnace coke. It included coke from all the current foundry coke producers. No available cupola studies have ex- amined the importance of the additional properties used for testing blast furnace coke (petrographic analysis, reactivity, abrasion resistance, degree of graphitization, ash melting point and ash catalyst index). The proposed study proposal will be the first to examine the importance of these additional properties.

International Journal of Metalcasting/Spring 2012

Given below are a number of potential improvements in coke performance that are conceptually possible. The analy- ses of coke in this proposed study should identify which concepts should most profitably be pursued.

1. Reduce CO formation as it produces less energy and more emissions than CO2.

2. Reduce the abrasive loss of coke. 3. Reduce the melting point of coke ash to increase car- bon dissolution in iron.

4. Produce alloys in-situ, e.g. SiC or Mn. Thermodynam- ics indicates it is possible.

5. Determine if coke properties, not currently measured, will provide new insight into coke’s performance.

Status Update: The project has just started. The work is being monitored by the AFS Melting Methods & Materials Cupola Committee (8F). Those wishing more information should con- tact Sy Katz, at

New Approaches to Clay Control in Green Sand (11-12#03)

Coordinator: Dr. Sam Ramrattan, Western Michigan University and AFS Molding Methods & Materials Committee (4-H)

Measurement of live clay in molding sand is critical to control of foundry green sand. Live clay levels must be controlled to develop and maintain proper strength levels and mechanical properties of the molding sand. Control of the live clay level is also critical to control of moisture and compactability because clay is the primary moisture absorber in molding sand. If clay level could be better controlled, the moisture and compactabil- ity could be more closely controlled. Inadequate control of compactability is the leading cause of green sand casting de- fects, and the associated costs of scrap, rework, labor, and en- ergy to individual foundries and the industry as whole warrant investigations into alternative methods of control.

The foundry industry needs a faster, more accurate, and low cost alternative to properly measure active clay in green sand. The Methylene Blue Clay techniques employed by the foundry in- dustry for measuring active clay suffer poor reproducibility and are thus incapable of maintaining accuracy. Casting defects are consistently attributed to variations in green sand systems and limitations of the clay control methods for green sand. A better clay measurement and control program is necessary to improve green sand systems. Western Michigan University has a new set of tests that can be used as process control tools to characterize and measure clays in green sand. This study explores the appli- cability of these tests to measure and control clay in green sand.

The AFS 4-H Green Sand Additives and Testing Commit- tee has been interested in finding a replacement for the Methylene Blue Clay Test as well as in studies of the heat damage to clays. The purpose of this study is to determine the effectiveness of using alternative in-process tests for measuring active clay in green sand while simultaneously studying the heat damage to clays.


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